CVE 2023-37207
A website could have obscured the fullscreen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 115, Firefox ESR < 102.13, and Thunderbird < 102.13.
See the 
CVE page on Mitre.org
for more details.
